I ran across the same information you did. The biggest hint that 5.8.0 (build 804) is no longer in beta is the announcement of the release of PDK 5.0 with ActivePerl 5.8 support. My guess is that when 5.6.1 gets removed an announcement will be made regarding 5.8.0.

Acolyte
Studying at the feet of the masters

Update: Still no "offical" announcement by ActiveState, but there are release notes for 5.8.0 here